School shootings, such as those at Columbine and Sandy Hook, plague the national consciousness and highlight deficiencies in preparedness and response to such tragedies. The present concepts seek to provide more effective means to protect our children and teachers. Existing technology, developed for military applications and environments, is not suited for application in schools, nor are they affordable to civilians.
In a conventional gunshot locating system, a plurality of sensors are situated in the field, usually at fairly regular intervals along an x-y grid. Each sensor includes a microphone and, presumably, an amplifier to produce an audio signal. The audio signal is then carried by a dedicated telephone line to a central location where the sound is processed. Upon detecting a gunshot from the processed audio, relative times of arrivals at the central location are processed to determine a location of the source of the gunshot.
In another known method for identifying the location of a gunshot, a special sensor having several microphones arranged in a geometric array is used and a radial direction can be determined by measuring the differences in arrival times at the various microphones. Unfortunately, such systems suffer from limited accuracy in the determination of the radial angle, which in turn, translates into significant errors in the positional accuracy of the source of the noise when triangulation of two or more sensors is performed. Since errors in the radial angle result in ever increasing position error as the distance from the sensor to the source increases, the reported position will be especially suspect toward the outer limits of the sensor's range.
Yet another type of gunshot sensor detects a gunshot and attempts to identify a particular type of weapon, or at least a class of weapon. These systems generally analyze the duration, envelope, or spectral content of a gunshot and compare the results to known samples.
U.S. Pat. No. 6,847,587, incorporated herein by reference in its entirety, discloses a system and method for detecting, identifying, and fixing the location of the source of an acoustic event, the system and method including a plurality of sensors dispersed at some-what regular intervals throughout a monitored area, a communication network adapted to deliver information from the sensors to a host processor, and a process within the host processor for determining, from the absolute times of arrival of an event at two or more sensors, a position of the source of the event. Acoustic events are detected and analyzed at each sensor so that the sensor transmits over the network an identifier for the sensor, an identifier for the type of event, and a precise absolute time of arrival of the event at the sensor.
U.S. Pat. No. 7,203,132, incorporated herein by reference in its entirety, discloses an acoustic event location and classification system comprising an array of at least two acoustic transducers arranged spaced from one another, a central data processing unit for receiving signals from the acoustic transducers and processing the signals to determine an event type and location, and an internet or LAN connection for transmitting event type and location data to a third party, wherein the central data processing unit uses a DSNN to determine the event type and generalized cross correlation functions between microphone pairs to determine the event location.
U.S. Pat. No. 7,411,865, incorporated herein by reference in its entirety, discloses a system and method for archiving and retrieving gunshot detection and location information from an array of remote sensors and preserving audio information surrounding a gunshot event for later review or analysis.
U.S. Pat. No. 7,688,679, incorporated herein by reference in its entirety, discloses a system for locating and identifying an acoustic event, such as gunfire, employing a plurality of wearable acoustic sensors, with each acoustic sensor having a display associated therewith for displaying information concerning the acoustic event to a user. The sensor includes a microphone for receiving acoustic information, an A/D converter, a processor for processing the digitized signal to detect a gunshot and determine a time of arrival, a GPS receiver for determining the position of the acoustic sensor, and a network interface for bidirectional communication with a system server.
U.S. Pat. No. 7,961,550, incorporated herein by reference in its entirety, discloses a systems and method for processing signals, particularly gunshot acoustic signals, the method including transforming initial bullet data associated with one or more sensors into a set of discrete pulses, dividing the discrete pulses into pulse subsets, generating, for the subsets, time domain representations of the pulses, wherein the time domain representations include waveforms having pulse features, and processing the time domain representations to determine alignment between one or more of pulse features, pulses, pairs of channels, and/or pairs of sensors.
U.S. Pat. No. 8,351,297, incorporated herein by reference in its entirety, discloses systems and methods for processing information associated with monitoring persons/devices and weapon fire location information. A weapon fire location system is used to characterize and locate impulsive events and these locations are correlated with the positions of monitoring persons or devices, such as monitoring anklets placed on offenders.
U.S. Pat. No. 8,325,562, incorporated herein by reference in its entirety, discloses a survey method for measuring signal propagation from an acoustic event in an urban setting with a distributed array in the midst of many buildings. A survey or tour of the covered region uses a moving signal source to probe propagation inside the region. Survey results may indicate where more sensors are needed.
U.S. Pat. No. 8,325,563, incorporated herein by reference in its entirety, discloses a system and method for locating a source of an acoustic transient, such as a gunshot, explosion, weapons launch, etc. The method is said to permit locating of the acoustic transient from a combination of propagation phenomena including a discharge time of the weapon fire incident. Moreover, the method may include obtaining a first propagation parameter of the incident from one or more first sensors, obtaining the discharge time from another sensor, and processing the data to determine a location using a common time basis among sensor measurements.